It has been possible hitherto to provide a number—dependent on the optical waveguide diameter—of light sources directly upstream of the optical waveguide, so that the light from the light sources is coupled into the optical waveguide. If more light sources are required e.g. in order to increase the brightness or for colour mixing purposes, it is already known to expand the end of the optical waveguide on the light source side in a funnel-shaped manner in order to increase the available coupling-in area at the end of the optical waveguide.
However, if the optical waveguide is expanded in a funnel-shaped manner on the light source side, the efficiency suffers since it is no longer the case that all the light beams obey the conditions of total reflection.
The situation is the same when the optical waveguide is split into a plurality of coupling-in strands on the light source side. Although a sufficient number of light sources can be arranged at the end areas of the coupling-in strands, losses likewise occur at the connecting points of the coupling-in strands with respect to one another and with respect to the optical waveguide.